Therapeutic substances



pounds of the types Patented Nov. 14, 1944 um'rao STATES PATENT OFFICE THERAPEUTIC SUBSTANCES Joseph R. Stevens, Plalnfleld, and Ralph H. Beutel, Newark, N. 3., 1110., Railway, N J0 assignors to Merck & 00., a corporation of New Jersey No Drawing. Application December 6, 1940,

Serial No. 368,844

4 Claims. (Cl. 260-479) This invention relates to substances having a physostigmine-like action, intermediates and processes for their production.

Phusostiymine H E CH: CHa-N- 0 However, physostigmine is subject to certain serious disadvantages, among them being that some of its actions are quite severe and at times rather unpredictable. Also the compound is relatively unstable so that care must be exercised in its use and preparation for use in order to avoid decomposition. For these reasons considerable efiort has been expended in an attempt to find compounds having an action similar to physostigmine but not-having its marked disadvantages.

Stedman (Biochemical Journal, vol. 20, 1926, p. 720) in the course of study found that commcnmx O O-l-NH-CH:

III

bamic acid esters of phenol also possessed activity and were much more stable.

We have now found that nuclear alkyl groups of amino phenols. This is true whether the amino group is ortho, meta, or para to the carbamic acid group and is also true regardless of the position of the nuclear alkyl group with respect to the amino group and the carbamic acid group. Particularly active are carbamic acid esters of p-amino phenols, in which alkyl groups are substituted in ortho position to the amino or carbamic acid group, or ortho to both the amino and carbamic acid groups. I'br example, the di-' methyl-carbamic acid ester of 3-isopropyl-4-dimethylamino phenol methiodide is 1600 times more active, therapeutically, than the corresponding carbamic acid esters of amino phenols in which alkyl groups are not substituted in the phenolic ring. 4

The new compounds oi our invention have the following general formula no 0 ON in which R is a nuclearly alkylated phenyl radical containing a dialkylamino group, R1 is alkyl or an aryl radical of the benzene series, and R2 is hydrogen, alkyl or an aryl radical of the benzene series.

According to our invention, these series of compounds may be prepared by coupling the desired alkyl-phenol with phenyl diazonium chloride, followed by reduction to produce an alkyl-amino phenol. This is methylated to form the corresponding dimethyl-amino-phenol from which the dimethyl carbamic acid ester is prepared by treatment of the phenol with dialkyl carbamyl halide in dry pyridine. The base can then be converted to a salt, for example, the hydrochloride, methiodide or methylsulfate by treatment with hydrogen chloride, methyl iodide, methyl sulfate and similar reagents.

Phenols which contain one or more alkyl groups such as carvacrol, thymol, cresol, and the like, may also be treated according to this process, for the preparation of carbamic acid esters of their amino derivatives. They may also be prepared by reacting the selected phenol with nitrous acid and reducing the thus obtained nitroso phenol to the amino phenol, which is then treated as described above for the production of the carbamic acid ester.

I iven by way of illustration and not 01 limitasubstituted in the phenyl radical aflect very markedly the therapeutic activity of monoor di-alkyl, or monoor-di-aryl carbamic acid esters tion, and that variations may be made therein without departing from the scope of the invention and the spirit of the appended claims. Thus,

ior example, while the invention is illustrated in terms of dimethylamino phenols it will be obvious that other dialkylamino phenols may be prepared -by the processes outlined, and by selecting the Forty g. 01 aniline are dissolved in a mixture of 104 g. concentrated hydrochloric acid and250 ml. water and diazotized with 30 g. sodium nitrite in 150 ml. water. The diazotized aniline is added to 53.7 g. m-ethyl phenol in 1000 ml. 01 6% sodium hydroxide at -5" with vigorous stirring and the mixture is allowed to stand /z hour. Aiter filtering oil. the insoluble material, the filtrate is acidified with sulfuric acid and extracted with ether. The extract is dried over sodium sulrate and the ether distilled off. The oily residue is taken up in methano1 and reduced catalytically in the presence of palladium oxide. After filtering, the methanol is distilled off until crystallization begin to take place. The concentrate is cooled in ice, filtered and washed with ether; yield, 44.5 g., 75% theory; recrystallized from ethanol, M. P. 169.5 C.

M-ETHYL r-Dnvrs'rnxr. AMINOPHENOL Eighteen 2. oil m-ethyl p-aminophenol are dissolved in 500 ml. ethanol, and g. of anhydrous sodium carbonate and 80 g. or methyl iodide are added. The mixture is refluxed for about 12 hours. The hot solution is filtered tree from excess sodium carbonate and concentrated until crystallization commences. The concentrate is cooled in ice, filtered, washed with a mixture or equal parts of ether and alcohol, and finally with ether. The quaternary salt thus obtained is destructively distilled under a pressure of 10-20 mm. in an oil bath at 220-250 C. The distillate is taken up in 10% sodium hydroxide, extracted with ether to remove alkali-insoluble products,

acidified with sulfuric acid and neutralized with sodium bicarbonate. The product is extracted with ether, and the extract is dried over sodium sulfate and concentrated; yield 6.5 3., theory.

The yield could be increased considerably at this point by refluxing the alkali-insoluble material with 57% hydriodic acid for several hours and working up as usual. In some cases, as much as of the yield is in the form or the methoxy compound.

DIME'mYL Cssssmc Acrn Earn 0! M-E'll-IYL P-DIMETHYLAMINO PHENOL HYDROCHLORIDE hydroxide solution is added. The mixture is sep-.

arated and the ether extract is washed several times with water. The extract is dried and distilled at 14 mm. to remove most of the pyridine. The oily residue is transferred to a Washburn molecular still and distilled in the vacuum oi a mercury vapor pump at yield, 7.5 2., 81% theory.

The thick paleyellow oil is dissolved in anhydrous ether and saturated with dry hydrogen chloride. The resulting crystals are filtered oil and washed with ether. They are recrystallized from a minimum amount or absolute alcohol by the slow addition of anhydrous ether. The crystals are washed with ether and dried in vacuo at 76; yield, 7.8 g., M. P. 141-3". Recrystallization gives 7 g., M. P. 1440-45.

DIMETHYL CARBsMrc ACID ESTER or M-ETHYL P-DIMETHYLAMINO PHENOL Mn'rrrronma a small amount of acetone. An excess of methyl I iodide is added and, after three days, several volumes of ether are added. The mixture is filtered and washed with ether, yielding 3.6 g. or the methlodide, M. P. 148-9". 0n evaporating down the mother liquors, taking-theresidue up in methyl iodide andstanding for 10 days, a further 2.8 g. are obtained; yield, 6.4 g., 97% theory. Recrystallization from alcohol and ether gives 6.2 g., M. P. 1485-95.

Using the method outlined above a number of other compounds were prepared. These new compounds are listed in Table I, and for convenience in comparing the activity of our new compounds with that or the dimethyl carbamic acid ester or p-dlmethylamino phenol, and with physostigmine, itself, these two last mentioned substances are also listed in Table I.

Table I Analysis L. D. 50 Compound. Dimethyl carbamic acid ester of- M. P in i 0 H N 01 I mam/kilo Degrees m-Mahyi-sdi ei ym p no y ocmo- 531;; 333 g; g m y -ll y P1181101 methiodidam $33? z: :3 mg 13,) m-Ethyl-p-dimethylamino phenol hydrochloride.. 33%;; 144-144. 5 45, 0 m-Ethyl-p-dimethylsmlno phenol methiodide gg k- 23:8 5 L15 m-Isopropyl-p-dimeth'ylsmino phenol methiodide. gg f g: 163-4 0. 075

P-mmethyhmino 131mm! 111931105159 2:8; 1:: 195. 5-196 Phy i i tls i gym- 18B 0, 54.

Certain new compounds have been prepared as intermediates in the Production or the compounds listed in Table I. These new intermediates are liven in Table H. a

Nrrsoso Cssvscnor.

One hundred gins. of carvacrol are dissolved in 100 cc. absolute ethanol, saturated with hydrogen chloride at Fifty-six gms. of sodium nitrite in concentrated aqueous solution are slowly added at 10 with vigorous stirring. The thick paste is diluted with several volumes of water and allowed to stand over night. This is filtered, washed with water and dried. Yield, 118 gms.

P-Aiurno CARvi cnor.

The nitroso carvacrol is dissolved in 2 l. of methanol and reduced with hydrogen in the presence oi 1 gm. platinum oxide under about 1 atm, pressure. The catalyst is'filtered oil and the filtrate distilled down on the steam bath to the start or crystallization. Several volumes of hot water are added, the mixture cooled in ice, filtered, the product washed with water and dried. Yield 100 g.

r-Dmrrnnsmmo Csnvscsor.

The p-amino carvacrol is dissolved in 1 l. methanol and refiuxedior 7 hours with '15 gms. of anhydrous sodium carbonate and 454 grns. methyl iodide. After standing overnight the mixture is cooled in ice, filtered, washed with isopropanol,

then ether, and dried.

The impure quaternary salt is distilled directly under vacuum at about 250-75. The distillate is taken up in benzene, filtered from any quaternary salt carried over, extracted with 10% NaOH and the alkaline solution acidified. Upon the addition of ammonium hydroxide the p-dimethylamino carvacrol crystallizes out. -Filtered,washed with water and dried. Yield, 40 gms. p-dimethylamino carvacrol.

. It the alkali-insoluble material is refluxed with hydriodic acid and worked up in the usual manner, the yield can be greatl increased at this point. This is due to the methylation of the hydroxy group in the methylation step.

DmarHYr. CARBAMIC Acm Esra]! or P-DIMETHYL- AMINO Cssvscnor. HYDROCHLORIDE times with 2% sodium hydroxide. dried and concentrated in vacuo. The crystalline residue is dissolved in ether and converted to the hydrochloride by passing dry hydrogen chloride-into the ether solution. Filtered, washed with ether and dried. M. P. 185.

Dnu'rmn. Cessemc Acre Esrrn or s-Drurrmrn- AMINO Csnvllcsor. Mnrnronma trated in vacuo. An excess or methyl iodide is added to the residue and the mixture allowed to stand several days; filtered, recrystallized from methanol-ether, from ethanol and finally from CHaOHEt:O; Yield, 40 3111s.: M. P., 172.5".

EXAMPLE III Thymol is treated according to the above procedure to produce the dimethyl carbamic acid ester of p-dimethylamino thymol hydrochloride and methiodide.

New compounds prepared are listed in Tables III and IV.

Table III Analysis I C0l1gp0l}nd.h]i)lmt:th};lcar- M P 331 am cac es ro- Cale. Found mgm/kg' p-Dimethylamino thyznol methiodide Dewzea N..- 6.89 6. 89 171.6 0. 72 p-Dlmeth lamina carvecrol met iodide 173.5 0.2-1 N 6.89 6.97 p-Dimethylamino thyinol dimethyl urethane hydrochloride N 9. 32 9. 26 170 160 p-Dimethylamino carvecrol dimethyl urethane hydrochloride Table I V Analysis Compound M. P

Calc. Found p-gmethylamino thymol hydrochlo- Deqrega -4 N 6.10 6. 21 p-rllJmethylamino carvacrol hydrochlo- EXAMPLE 1v o-Aiumo P-CRESOL o-Drmnnammo r-Cnssor.

- Twenty-eight gm. of o-amino p-cresol are dissolved in cc. methanol and gms. methyl iodide and 30 gms. anhydrous sodium carbonate added. After the reaction subsides, it is refluxed for about three hours. The mixture is cooled.

filtered, and the product washed with ether and DnurnvLcsssn/nc Acrn Es'rsa or o-Dmrrnnsumo r-Carsor. Hrunocntoarnr Three gms. oi o-dimethylamino p-cresol are dissolved'in 6 gms. pyridine and 2.78 gms. dimethyl carbamyl chloride added. After heating on the steam-bath overnight the excess pyridine is distilled off in vacuo and the residue distilled in a molecular still at 110 at 10-* mm. The distillate is taken up in ether and converted to the hydrochloride by passing in dry hydrogen chloride. The product is filtered ofl, washed. with ether, and dried. Yield, 2.34 gms.

Drm'mrncssssmc Acre Earns OFO-DIHITRYL- Aismo r-Cansor. Mari-norms The hydrochloride is dissolved in water, made alkaline with ammonia and extracted with ether.

, Tsrtiarybut io-dih'diiirfiifi'hsndf hydroohlorid e -3 -3 During thecourse oi this work the new compounds listed in Table VII were prepared.

. Table VII Anal Compound m M. P.

Oalc. Found p-Ethyl-o-pmim ghenol. 130.8,

O 'p-Tertiary bntyl o-smino phanoL- p-Tertiary amyllg-dimethylamlno phenol- The p-isopropyl phenol for the p-isopropyl derivative was prepared as follows:

P-ISOPROPYL ANILINI A mixture of 100 gms. of nitric acid (d. 1.44) and 150 gms. concentrated sulfuric acid is added slowly with stirring at 20-30 to 100 gms. cumene. When all of the acid is added, the cooling bath is, removed and the temperature allowed to rise Concentrated, added an excess of methyl iodide to the residue and let stand for about twelve hours. The crystalline mass is triturated with ether, filtered, washed with ether, dried; recrystallized twice from EtOH-EtsO.

The new compounds listed in Table VI are prepared according to this process.

Table VI Com und. Amy! L. n. m Dimethy csrbamic M. P inmice acid ester 01- Cale. Found mgmJkg o-Dlmethylamino g methyl phenol met iodide 154.5 2

42.8 03.2 H as: v 5.51 o-Dimethylsmino egg 'l phenol met i de 14841 1.26

88.0 03.4 o-Dimethylamino piso r 3; 1 phenol met 1 1a.... 171 4.8

O 45.9 40.8 H 6.42 6.36 o-Dimethylamino ptertiary butyl'phenoi methiod e..... 102 13.5

81.2 31.2 o-Dimethylamino ptertiary amyl phenol methiodide-.. 146.5 12.0

30. 2 S0. 1 o-Dimethylamino pmath lphenolhydrochlor de 174. ii 210 C..'- 55.7 55.4 H 7. 41 7.13 o-Dimeth lamino pethyl p enol hydrochloride 144-5 27 13.0 13. 1 u-Dlmethylamino piso ropyl phenol hy ochloride 108.6 400 Cl 12.4 12.4 o-Dimethylamino ptertiary but lpbenol hydrochlori e 180.6 500 11.8 11.8 o-Dimethylamino ptertlary am lphenoi hydrochlori e Hat-176.0 500 Cl 11.3 ll.

to 40. When there is no further rise in temperature, the mixture is poured onto ice, diluted The extract is washed with sodium bicarbonate solution and dried. The ether is distilled oil and the residue taken up in methanol and reduced with hydrogen, using platinum oxide catalyst. The alcohol is distilled oil, the residue dissolved in ether and extracted with hydrochloric acid. The acid extract is made alkaline with sodium hydroxide and extracted with ether. The ether is distilled of! and the residue added to a boiling solution or 100 gms. oxalic acid in 1 1. water. The solution is decolorized with charcoal, filtered hot and cooled in ice to 10. The product is filtered Thirty-tour gms. of p-isopropyl aniline are suspended in 62.5 gms. conc. sulfuricacid and 500 cc. water. 17.3 gms. of sodium nitrite in cc. water are added at 0 C. The excess nitrous acid is destroyed with urea and the mixture heated at 50-60 for several hours. The solution is cooled, extracted with benzene, the benzene so- .lution extracted with 10% sodium hydroxide, the

alkaline solution acidified and extracted with benzene. Upon distilling oil the benzene, the residue crystallizes immediately on cooling. Distillation at atmospheric pressure gave 25 gms. oi p-isopropyl phenol.

EXAMPLE V r-Arsmo o-Carsox.

Sixty-eight gms; oi o-cresol are dissolved in 2'70 cc. 10% sodium hydroxide and to this is added a solution of a diozotized aniline from 60 gms. aniline in 132 cc. conc. hydrochloric acid and 200 cc. water and 240 cc. 20% sodium nitrite at The material is filtered, acidified with acetic acid, the dye filtered off and dried. The filtrate is dissolved in hot benzene, petroleum ether is added, cooled, filtered, dried. Yield, 43.5

The yield is dissolved in methanol and reduced with hydrogen, using platinum oxide catalyst. The catalyst is filtered oil, the filtrate concentrated, cooled in ice, filtered, washed with petroleum ether, dried. Yield, 14 gms. p-amino o-cresol; M. P. 173.

P-DIMETHYLAMINO O-CRESOL DnnrrHYL CARBAMIC Acm Es'raa 0F P-DIMETHYL- AMINO o-Cmrsor. HYDROCHLORIDE Three gm, of the base are dissolved in 6 gms. pyridine and 2.78 gms. dimethyl carbamyl chloride added. The mixture is heated for about twelve hours on the steam bath, after which the excess pyridine is distilled off in vacuo. The residue is taken up in ether, washed several times with 2% NaOH and concentrated.

The concentrate is distilled at 110 in a molecu lar still at 10- mm. The distillate is dissolved in ether and hydrogen chloride passed in. It is filtered and recrystallized from EtOH-EtaO.

-The extract is concentrated, and an excess of the material is filtered, and the filtrate recrys- The dimethyl carbamic acid ester of p-dimethylamino o-cresol hydrochloride of melting point 189 is obtained.

Calc.: O, 55.7%; H, 7.41%; found: C, 55.5%;

Dun-ran CAiiBAMIC Acm Es'rrm or P-DmsraYL- Ammo o-Cuasor. Msrmonroz The hydrochloride is dissolved in water,made alkaline with ammonia and extracted with ether.

methyl iodide added and the mixture allowed to stand for about 12 hours. Ether is added, and

tallized twice from EtOH-EtaO. The dimethyl carbamic acid ester of p-dimethyl-amino o-cresol methiodide of melting point 189-190 is obtained. l

0010.: 0 42.89"]! 5.517 Found: 0143.0 ,5 B1 5.00% %11- mgm-lklm- We claim:

1. The dimethyl carbamic acid ester of p-dimethyl-amino thymol methiodide.

2. The dimethyl carbamic acid ester of p-dimethyl-amino,m-isopropyl phenol methiodide.

3; The dimethyl carbamic acid ester of p-dimethylamino carvacrol methiodide.

'4. A substance selected from the class consisting of compounds of the formula where R is one of the group CH3 and hydrogen,

- and quaternary salts thereof.

JOSEPH R. STEVENS. RALPH H. BEUTEL. 

